Pop-up ads annoying; doesn't show "circle," no "interaction." I would NOT use this tool to demonstrate... I can draw better examples myself, and make them fit what I was doing in class. Even static drawings in a textbook would be as good.

This material is based upon work supported by the
National Science Foundation under Grant DUE-0226284.
Any opinions, findings, and conclusions or recommendations
expressed in this material are those of the author(s)
and do not necessarily reflect the views of the
National Science Foundation.